JP2005176036A - Image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accelerate an image processing, to improve image quality and to reduce a memory. <P>SOLUTION: An image processor is provided with a variable power rate calculation means for calculating a required variable power rate from an input image size and an output image size, a combining means for combining input image data, a reduction means for reducing combined image information, an enlargement means for enlarging the image information, and a color transformation means for transforming the signal value of input images to a color space suited to an output device and generating density image signals. In the image processor, in the case that the variable power rate obtained by the variable power rate calculation means is reduction, a reduction processing is performed to the combined input data at a reduction ratio, which is the maximum reduction rate not exceeding the obtained variable power rate and for which the reduction rate in respective vertical and horizontal directions is 1/2<SP>n</SP>(1 to n-th power of 2), the color transformation processing is performed to the reduced data, then the magnification processing is performed, and thus required output data are obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image processing apparatus that performs color conversion processing, enlargement or reduction processing, etc., on an input color image signal. The present invention relates to an image processing program mounted on a storage medium storing a control program for controlling the recording apparatus in a recording apparatus that records recording information.

  In general, a digital image recorded by an input device represented by a digital camera is recorded in a size unique to the input device. In the printing device that outputs the digital image, the size of the output print medium, the output size of how many images are output on one medium, and the resolution at which the color processing is performed, etc. The size is determined by both the resolution specific to the output device.

For example, when printing an image with an input device size of 2560 pixels wide and 1920 pixels high on a 6 x 4 x 4 inch print medium called 4x6, the color resolution of the output device is It is assumed that it is 300 DPI (Dot Per Inch). In this case, since the output size viewed from the output device is 1800 pixels wide and 1200 pixels high, the input image is subjected to reduction processing, a portion protruding in the vertical direction is cut out, color processing is performed, and output is performed. (For example, Patent Document 1)
No. 06-014285

  However, the conventional example described above has some problems with respect to enlargement / reduction processing in terms of memory capacity, processing speed, and image quality.

  First, there is a problem of the capacity of a storage device that holds an image. In general, an input image is encoded based on an image format represented by JPEG and recorded on a recording medium. Therefore, the image size output from the decoding unit that decodes this image format and obtains the original signal value is the original recorded image size, and is then subjected to scaling processing by a scaling processing unit such as enlargement or reduction .

  Therefore, it is necessary to have a capacity of a storage device that can hold a composite input signal value once. For example, in the case of the above-mentioned example, the output device can output with a storage device capacity of 1200 pixels in the vertical direction, but since the number of pixels on the input device side is large, a storage device capacity of 1920 pixels is required, and the output device As such, it required unnecessary storage capacity.

  Second, there is a problem in sampling called aliasing distortion. In general, a nearest neighbor method, a bilinear method, and a cubic convolution method are known as enlargement / reduction algorithms. These interpolation methods are based on interpolation based on the sinc function {sinc (x) / x} based on the sampling theorem, and an interpolation function approximating the sinc function is reduced to the original image in order to reduce the computational load. The number of pixels is increased or decreased by interpolating between the sample points of the original image.

  The nearest neighbor method is a method in which a rectangular function is used as an interpolation function and the value of the nearest sample is used as an output interpolation value. It is known that the nearest neighbor method can be realized by an extremely simple logic operation. On the other hand, at the time of reduction, the high-frequency component causes image degradation called aliasing distortion. As a method for avoiding the aliasing distortion, a method of removing high-frequency components by a low-pass filter is generally used. However, since a processing load is applied, the high-speed processing characteristic of the nearest neighbor is impaired.

  Thirdly, there is a problem of image processing speed. Even if the nearest neighbor method is used for speeding up, low-pass filter processing is required to remove aliasing distortion, which hinders speeding up of processing as described above. There is a factor that hinders the speedup. As described above, in order to perform enlargement / reduction processing after composite processing, a recording area for holding the input signal value after composite must be prepared, but the composite processing is performed without preparing this storage area. It is also conceivable to perform processing and scaling processing at the same time. However, in this method, since output processing is performed by performing color processing unique to the output device after scaling processing, in the case of enlargement processing, the number of processing pixels for performing color processing unique to the output device increases. Therefore, there arises a problem that the image processing speed is reduced.

  Further, when the enlargement process and the reduction process are executed prior to the color process, if the enlargement process is performed, the processing target pixels increase due to the enlargement process, leading to a reduction in processing speed. Further, even when the processing is executed after the color processing, if the reduction is performed, the processing speed may be reduced.

  The present invention has been made in view of the above-described problems of the prior art described above. The object of the present invention is to enable output with the minimum storage capacity regardless of the input device and cause image degradation. It is an object of the present invention to provide a printing method that performs color processing for output at high speed with no image processing method.

The present invention is for solving the above-mentioned problem, a scaling factor calculating unit that calculates a necessary scaling factor from an input image size and an output image size, a compounding unit that combines input image data, Reduction means for reducing composite image information, enlargement means for enlarging image information, and color conversion means for converting a signal value of an input image into a color space suitable for an output device and generating a density image signal In the image processing apparatus provided, when the scaling factor determined by the scaling factor calculation means is a reduction, it is the maximum reduction ratio that does not exceed the determined scaling factor for the combined input data, and By performing the reduction process at a reduction ratio of 1/2 ⁿ in the vertical and horizontal directions, performing the above color conversion process on the above reduced data, and then performing the above enlargement process, Necessary output data This is an image processing method characterized by obtaining data.

  As described above in detail, according to the recording method and apparatus of the present invention, it is possible to output with a minimum storage capacity regardless of the input device, and to output at high speed using an image processing method that does not cause image degradation. It is to provide a printing method for performing color processing.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing the configuration of an ink jet recording apparatus (printer) according to an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a control unit that controls the recording apparatus. Reference numeral 11 denotes an I / F (interface) unit. The I / F unit 11 is connected to a memory card that holds image data captured by a digital camera or a digital camera, and the main body control unit digitally converts the image data to be printed. Read from the camera or memory card and send to 12 image processing units. An image processing unit 12 performs image data decoding processing, reduction processing, and color processing on the recording data (multi-valued image data) sent from the I / F unit 11, and includes memory, ASIC (Application Specific). It is composed of an integrated circuit (IC) for specific applications, a DSP (Digital Signal Processor), a RISC (Reduced Instruction Set Computer) chip, and the like.

  FIG. 2 is a block diagram showing the internal structure of the image processing unit shown as 12 in FIG. In this embodiment, each process is realized by software as an independent task. The function of each processing block will be described while briefly explaining the flow of processing.

Reference numeral 21 denotes a decryption / reduction processing unit. The input image data is decoded by the decoding / reduction processing unit, converted into signal values such as Y, Cb, Cr, R, G, and B, and recorded on the pixels of the recorded image and accordingly sequentially expanded in the memory. Go. In the case of reduction processing, the decoding / reduction processing unit performs reduction processing at a necessary reduction rate. In the reduction processing, processing is performed only by reduction at a certain reduction rate in order to increase the processing speed, and the result is developed in a memory. The constant reduction ratio is 50%, 25%, 12.5%,. . . And 1/2 ⁿ reduction processing. With this reduction rate processing, it can be easily implemented using only division by addition and shift operations, and processing can be performed at high speed. The data subjected to the decoding process and the reduction process described above is stored in the buffer 26. Here, since the reduction process is performed, the actual image frequency has dropped to half, so the effect of the low-pass filter can be obtained.

  Next, the data stored in the buffer 26 is read from the 23 color processing units. The color processing unit converts the image data stored as the luminance data into density data. Since the reduction is performed more than necessary reduction processing, the number of pixels to be subjected to color processing can be reduced, so that the color processing can be speeded up. The output of the color processing unit is passed directly to 24 enlargement processing units, and after necessary enlargement processing is performed in the enlargement processing unit, it is stored in 27 output buffers. Thereafter, although not shown in the figure, error diffusion processing is performed and binarized, and then transmitted to the print head.

  The process flow has been briefly described above. Next, the process will be described in detail with a specific example.

  The input data is image data encoded in a format called JPEG, and its size is 2560x1920 in both vertical and horizontal directions. Assuming that the image data stored in the PC card is stored, the color processing resolution of the output device is 300 DPI, and the output setting value set by the user is the same on a 4 × 6 inch output medium. A description will be given on the assumption that a single image is fully stretched and output without any margins.

First, a scaling factor is calculated by a scaling factor calculator shown in FIG. In this case, since the input data is 2560 × 1920 and the output is 4 × 6 inches 300 DPI, if the long side of the print medium is aligned with the long side of the image, the number of pixels becomes 1800 × 1200. The horizontal and vertical enlargement / reduction ratios are 1800/2560 = 0.703125, 1200/1920 = 0.625. In order to print without borders, the reduction conversion is 0.703125 as the enlargement / reduction ratio, and the remainder in the vertical direction is cut off. Here, in the case of the reduction process, the scaling factor calculation unit instructs the reduction processing unit to use a reduction rate that does not exceed a desired reduction rate and a reduction rate of 1/2 ⁿ . The reduction ratio in this case is 0.5 (1/2 ⁿ ), which is a reduction ratio that satisfies the above-described conditions, so 0.5 is instructed to the reduction processing unit. Further, since the reduction rate processing unit performs processing at this reduction rate, the scaling factor calculation unit recalculates the enlargement rate for enlarging to a necessary size from this reduction rate. In this case, since an enlargement ratio for enlarging an image reduced to 0.5 to a desired reduction ratio of 0.703125 is necessary, the enlargement ratio is 0.703125 / 0.5 = 1.40625. By instructing the enlargement factor obtained here to the enlargement factor calculator, the input image is reduced by 1/2 ⁿ , then enlarged by the enlargement processor, and converted to the required output image size. Is done.

Next, the decoding processing unit acquires data to be printed through the interface unit and performs decoding processing. Here, since it is a reduction process, the decoded image is not stored in the input buffer as it is, but is stored after the reduction process in the reduction processing unit. In the reduction process, after one pixel is decoded, the obtained value is subjected to a shift operation according to the reduction rate. In this case, 1-bit shift is performed. Next, it is determined whether the necessary number of pixels have been decoded. In this case, since two pixels are required in the horizontal direction, the pixel value is obtained once again and shifted in the same manner as before. Although this processing proceeds in the horizontal direction, in this embodiment, since it is a JPEG format, 8 × 8 pixels are combined as a basic unit (MCU). Decode processing. The second row is processed in the same manner as before. Here, since the decoding of 1/2 pixel is completed, it is written to the input buffer. By proceeding with the same process, the process of decomposing and reducing is performed. Here, the same effect as the low-pass filter can be obtained by performing the reduction process of 1 / ²ⁿ .

  Next, the color processing unit performs processing. The color processing unit converts the Y, Cb, and Cr luminance data obtained by decoding the JPEG format image file into cyan, magenta, and yellow used in the printer of this embodiment. The converted data is once stored in the intermediate buffer.

Next, the enlargement processing unit acquires processed data from the intermediate buffer, performs enlargement processing, and passes it to the error diffusion processing unit. In the present embodiment, the above-described bilinear complementary operation is implemented. The data string that has undergone the enlargement process is passed to the binarization processing unit, binarized by the error diffusion method, and passed to the print control unit.
The print data developed into a dot pattern at the final stage of processing in the image processing unit 12 is temporarily stored in the memory unit 14 by the memory controller. The memory unit 14 is composed of a memory of one band or more necessary for a recording head (not shown) to scan once in the main scanning direction and perform recording. In this embodiment, the recording head is in the sub-scanning direction. No. of nozzles is 128 nozzles, and the maximum number of dots that can be recorded in one scan in the main scanning direction is 8k dots.
128 (nozzles) x 8k (dots) x 4 (colors) = 4MBit
Will have a memory capacity of Further, writing / reading of print data to / from the memory unit 14 is performed by a memory controller under the control of the DSP or RISC chip of the image processing unit 12, and an address signal and write / read timing signal are transmitted to the memory unit 14. Is generated. Further, the reading of the print data from the memory unit 14 is output to the print head control unit 15. The print head control unit 15 generates an ink ejection timing signal and a heat pulse from the print head unit 17 based on the control of the control unit 10.

  The print head unit 17 includes a recording head corresponding to each color ink, and heats a heater unit by the control unit 10 and the print head control unit 15 to discharge the ink, thereby recording an image on a recording sheet. The print head unit 17 is actually mounted on the carriage of the motor drive unit 16. The motor driving unit 16 detects ink clogging of a carriage unit and a carriage driving unit for moving a recording head (not shown) in the main scanning direction, a recording sheet feeding unit, a recording sheet conveying unit, a recording sheet discharging unit, and a recording head. Consists of a recovery unit for recovery. An operation panel 18 includes switches for instructing paper feed, paper discharge, recording paper selection, and the like, and a display unit for displaying the status of the recording apparatus.

Through the above processing, print data is created and printing on the recording paper is performed.
In this embodiment, the bilinear method is implemented as the enlargement processing, but the present invention is not limited to this, and other enlargement processing algorithms (nearest neighbor method, cubic convolution method, etc.) may be used. Needless to say.

  In addition, the recording apparatus according to the present embodiment realizes the above-described functions of the present embodiment by causing a computer to read and execute a control program stored in a storage medium. The present embodiment is not limited to this, and part or all of actual processing such as an OS (operating system) running on the computer is performed based on an instruction of the control program, and the above-described embodiment is performed by the processing. It goes without saying that the case where the function is realized is also included.

  In addition, there are many cases where each processing unit is implemented not as software but as hardware, including image data decoding processing, but the present invention is not based on the implementation form of these processing units.

1 is an explanatory diagram of an ink jet recording apparatus according to a first embodiment of the present invention. 3 is a simple flowchart of image processing according to the present invention.

Explanation of symbols

10 Printer control program
11 Interface part with image file input device
12 Image processing section
13 Operation panel for user to instruct the printer to print
14 Memory for storing image information and memory control unit
15 Print head controller
16 Motor control unit for paper feeding and print head scanning
17 Print head
21 Decoding and reducing image files
22 Input image file receive buffer
23 Color processor that converts input image signals to output image signals
24 Enlargement processing section
25 Color processing unit for error diffusion
26 Intermediate buffer for storing image data in-process information
28 Scaling factor calculator that calculates the reduction ratio and enlargement ratio from the input image size and output image size

Claims (1)

A scaling factor calculating unit that calculates a necessary scaling factor from an input image size and an output image size, a compounding unit that combines input image data, a reduction unit that reduces the combined image information, and image information In an image processing apparatus comprising an enlarging means for enlarging and a color converting means for converting a signal value of an input image into a color space suitable for an output device and generating a density image signal, the variable obtained by the scaling factor calculating means is obtained. When the magnification is reduction, the maximum reduction ratio that does not exceed the obtained scaling ratio is obtained for the combined input data, and the reduction ratio in each of the vertical and horizontal directions is 1/2 ⁿ . An image processing method characterized in that reduction processing is performed at a reduction ratio, and after performing the above-described color conversion processing on the above-described reduction data, the above-described enlargement processing is performed to obtain necessary output data.

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